1. Field of the Invention
The present invention relates to a technique for detecting approach of a person by using a sensor, and controlling an image forming apparatus. In particular, the present invention relates to control for detecting dust near a sensor attached to the image forming apparatus.
2. Description of the Related Art
When detecting approach of a person by a sensor and controlling an image forming apparatus, it is important to maintain the sensor in an effectively functioning state. For example, if dust adheres to the sensor, the sensor may fail to function effectively. To detect dust adhering to a sensor, a sensor of light emission type conventionally is used. The sensor emits light in a predetermined detection direction, and senses the reflected light to detect the dust. Japanese Patent Application Laid-Open No. 2013-101003 further discusses a technique for determining color of light that facilitates dust detection according to the reflected light obtained by the sensor, and emitting light of that color.
An infrared array sensor of non-light emission type detects infrared rays emitted from a heat source. If such a sensor of non-light emission type is used to control the image forming apparatus, dust detection similar to that of a conventional sensor of light emission type cannot be carried out. If an infrared light receiving unit of the infrared array sensor is blocked by dust, the infrared array sensor fails to detect a heat source, in which case it may become impossible to detect the approach of a person by using the sensor and control the image forming apparatus.